Where to do "huge" graph calculations - Flutter, php

Question

I'm planning on doing an application that create the shortest possible path to some interest points.
Each point is an activity separated from the other by a distance (e.g. p1 --50m--> p2). Later there will be a wait time for each point so it'll look like p1(5) --50m--> p2(15)
The user chooses his points and then the app create the shortest possible path to do every point the less walk to do for the user.
To accomplish that I though using a weighted graph (maybe a search-tree or something else should be better, I'm open to suggestions).
My question is that what's the better (faster) between doing the calculation for the path search : directly in the app (Flutter - dart) or on the server and then the app shall go get the result there ? Thanks for your help guys :D